In general, a casting is produced by forming a mold having a cavity therein using molding sand on the basis of a wooden mold or a metallic mold, disposing a core in the cavity as necessary, and thereafter supplying molten metal into the cavity.
To produce the wooden mold or the metallic mold, skill in the processing thereof is required, and an expensive facility is needed. Therefore, disadvantages such as high cost and heavy weight and problems in waste disposal occur, and thus it is difficult to use the molds for uses other than mass-produced castings. In addition, the shape of a sand mold, which uses molding sand, is retained by adding a binder to typical sand and hardening. Therefore, a regeneration treatment process is essential for reusing the sand. In addition, there is also a problem of the generation of waste such as dust during the regeneration treatment. Moreover, in a case of producing a core using the sand mold, in addition to the above problems, it is difficult to handle the core due to the mass of the core itself. In addition, conflicting characteristics such as a strength holding characteristic during casting and a core removing characteristic after casting are required.
As a technique to solve the problems, known are structures formed of members used in molds, such as an organic fiber, an inorganic fiber, and a thermosetting resin as primary components.
For example, in JP-A 2004-181472, a structure for producing a casting is disclosed which contains an organic fiber, an inorganic fiber, and a thermosetting resin such that the structure for producing a casting has good moldability and a light weight, and has sufficient hot strength and shape retention during casting, allows the obtained casting to have excellent shape retention and surface smoothness, and has excellent removability after casting.
In JP-A 2005-349428, a structure for producing a casting is disclosed which contains an organic fiber, a carbon fiber, inorganic particles, and at least one type of thermosetting resin selected from a phenolic resin, an epoxy resin, and a furan resin such that the structure for producing a casting has good moldability, has sufficient hot strength and shape retention during casting even when the weight thereof is light, allows the obtained casting to have excellent shape retention and surface smoothness, and has excellent removability after casting.
In JP-A 2007-21578, a structure for producing a casting is disclosed which is configured to include a structure (I) containing an organic fiber, an inorganic fiber, and a binder, and inorganic particles which have an average particle diameter of 1 nm to 800 nm and adhere to the surface of the structure (I) such that gas defects as casting quality can be improved.